The present invention relates to an ignition timing control device of an internal combustion engine.
An ignition timing control device is known, in which the ignition timing is maintained at an optimum ignition timing when a knocking does not occur, but the ignition timing is retarded relative to the optimum ignition timing when the knocking occurs. In such a conventional ignition timing device, the level of vacuum produced in the intake manifold or the amount of air fed into the cylinder of the engine is normally detected by a diaphragm type sensor or an air flow meter, respectively, and the ignition timing is controlled based on the result of the detection. In an engine, when the engine is abruptly accelerated from a light load operating state, the level of vacuum in the intake manifold abruptly becomes small, and the amount of air fed into the cylinder of the engine is abruptly increased. However, at this time, in a conventional ignition timing device, since the delay of detection is present in the diaphragm type sensor and the air flow meter, the ignition timing is temporarily maintained at an ignition timing which is optimum in the light load operating state immediately after the engine is abruptly accelerated. Nevertheless, since the optimum ignition timing in the light load operating state is considerably advanced relative to the optimum ignition timing in the heavy load operating state, the actual ignition timing is considerably advanced relative to the optimum ignition timing actually required for the engine immediately after the engine is abruptly accelerated. Consequently, at this time, even if the ignition timing is retarded in response to the initial occurrence of a knocking, it is difficult to suppress the successive occurrence of a knocking. This results in a continuous occurrence of knockings.
In addition, in a conventional ignition timing control device, the ignition timing is retarded everytime a knocking occurs. Consequently, when the diaphragm type sensor or the air flow meter produces an output signal which correctly indicates the level of vacuum in the intake manifold or the amount of air fed into the cylinder of the engine, respectively, a little while after the engine is abruptly accelerated, the ignition timing is considerably retarded relative to the optimum ignition timing which is actually required for the engine. As a result of this, a problem occurs in that the drivability of a vehicle and the specific fuel consumption deteriorate.